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Well in that case, I take back the "ugly". Enjoy the free TV!
 

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I am sure eveyone has seen this commercial of the guy on the Carribean with this antenna?

Well, a friend I haven't seen in a while had one of these. His wife was using it on a smallish TV, so I gave him my old LG 42" LCD, and the LG sadly didn't receive all the same stations as the smallish TV did with the same antenna in the same spot. So I gave him a home made biquad to stick in the picture window and his TV works great now.

So, I wanted to see what made that thing tick, attempting to model it with NEC2. A bit of a hack, but I think is about as good as I can make it, not being an expert antenna modeller, like some of the other people around here.
Here is a photo of it.
11382
 

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It is basically just a 4 whisker bowtie, with some funky loops above and below.
It seems to have a sharp null right at 527 MHz, Ch 23. I don't know if that's just my crappy hack of a model or not.
But that does seem to jive with ~ 1/2 wavelength at 527 MHz, approx the width of them two loops. Included my hack of a model in case someone else wants to take a crack at it, just for kicks. Far as I can tell it would be better off without them two loops. And the Whiskers aren't anywhere near long enough for today's UHF frequencies. Admittedly I have no idea what is inside that little plastic the cable comes out of, I assume it is a small PC Board 300->75 ohm balun.

Model Link
UHF Sweep
nec2 model
Code:
CM UHF 4-Whisker 1-Bay Bowtie, BowSwp=0.0-in, NO Refl, 4nec2 by holl_ands, 20Apr2010
CM BowLength=10-in, TineSep=5.0-in (AWG10 Elements).
CM FeedSep=1.5-in (AWG10).  Simple SOURCE Wire.  AGT=1.0 (0.0 dB), No Errors or Warnings.
CM D--EVAL --vhf-hi --uhf-69 --centers --total-gain --char-impedance=300 --validate-geometry=0 --num-cores=2
CE
SY Rsource=0.0008
GW    1    3    0    -0.375    0    0    0.375    0    Rsource
GW    2    5    0    5.4    0.75    0    0.375    0    0.05094856
GW    3    5    0    -0.375    0    0    -5.4    0.75    0.05094856
GW    4    5    0    5.4    -0.75    0    0.375    0    0.05094856
GW    5    5    0    -0.375    0    0    -5.4    -0.75    0.05094856
GW    6    11    0    -5.4    1.35    0    5.4    1.35    0.05094856
GW    7    11    0    -5.4    -1.35    0    5.4    -1.35    0.05094856
GW    8    1    0    -0.375    0    0    -0.375    0.25    0.05094856
GW    9    1    0    -0.375    0    0    -0.375    -0.25    0.05094856
GW    10    1    0    0.375    0    0    0.375    0.25    0.05094856
GW    11    1    0    0.375    0    0    0.375    -0.25    0.05094856
GW    12    1    0    -5.4    1.35    0    -5.4    1    0.05094856
GW    13    1    0    -5.4    -1.35    0    -5.4    -1    0.05094856
GW    15    1    0    5.4    -1.35    0    5.4    -1    0.05094856
GW    16    1    0    5.4    1    0    5.4    1.35    0.05094856
GW    17    5    0    -5.4    1    0    -0.375    0.25    0.05094856
GW    18    5    0    0.375    0.25    0    5.4    1    0.05094856
GW    19    5    0    -0.375    -0.25    0    -5.4    -1    0.05094856
GW    20    5    0    0.375    -0.25    0    5.4    -1    0.05094856
GW    21    1    0    -5.4    0.75    0    -5.4    -0.75    0.05094856
GW    22    3    0    5.4    0.75    0    5.4    -0.75    0.05094856
GS    0    0    0.0254        ' All in in.
GE    0
EK
LD    5    0    0    0    3.e7    0
EX    0    1    2    0    1    0
GN    -1
' FR Freq Sweep choices in order of increasing calculation time (fm holl_ands):
' FR 0 0 0 0 470 0              ' Fixed Freq
' FR 0 29 0 0 470 12              ' Freq Sweep 470-806 every 12 MHz - OLD UHF BAND
' FR 0 34 0 0 410 12            ' Freq Sweep 410-806 every 12 MHz - Even Wider Sweep
FR 0 39 0 0 470 6             ' Freq Sweep 470-698 every 6 MHz - PREFERRED FOR UHF
' FR 0 77 0 0 470 3             ' Freq Sweep 470-698 every 3 MHz
' FR 0 153 0 0 470 1.5          ' Freq Sweep 470-698 every 1.5 MHz
' FR 0 71 0 0 300 10            ' Freq Sweep 300-1000 every 10 MHz - WIDEBAND SWEEP
' FR Hi-VHF choices:
' FR 0 15 0 0 174 3             ' Freq Sweep 174-216 every 3 MHz
' FR 0 29 0 0 174 1.5           ' Freq Sweep 174-216 every 1.5 MHz - PREFERRED
' FR 0 43 0 0 174 1             ' Freq Sweep 174-216 every 1 MHz - Hi-Rez
' FR 0 26 0 0 150 6             ' Freq Sweep 150-300 every 6 MHz - WIDEBAND SWEEP
' FR Lo-VHF choices:
' FR 0 35 0 0 54 1              ' Frequency Sweep every 1 MHz for Ch2-6
' FR 0 36 0 0 75 1              ' Frequency Sweep every 1 MHz for Ch5 + Ch6 + FM
' FR 0 28 0 0 54 6              ' Wide Freq Sweep every 6 MHz for Ch2-13
' FR 0 64 0 0 54 12             ' Super Wide Freq Sweep 54-810 every 12 MHz
' RP choices in order of increasing calculation time:
' RP 0 1 1 1510 90 90 1 1 0 0   ' 1D Gain toward 0-deg Azimuth - SIDE GAIN
' RP 0 1 1 1510 90 0 1 1 0 0            ' 1D Gain toward 90-deg Azimuth - FORWARD GAIN
' RP 0 1 1 1510 90 180 1 1 0 0  ' 1D Gain toward 270-deg Azimuth - REVERSE GAIN
' RP 0 1 37 1510 90 0 1 5 0 0   ' 2D (Left only) Azimuthal Gain Slice
RP 0 1 73 1510 90 0 1 5 0 0             ' 2D Azimuthal Gain Slice - PREFERRED
' RP 0 73 1 1510 90 0 5 1 0 0   ' 2D Elevation Gain Slice
' RP 0 73 73 1510 90 0 5 5 0 0  ' 3D Lower Hemisphere reveals antenna (use Fixed Freq)
' RP 0 285 73 1510 90 0 5 5 0 0 ' 3D Full Coverage obscures antenna (use Fixed Freq)
EN
 

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The Televes designs from Spain are well known, as you can see in the Antenna R&D Forum threads devoted to them. In reality, there is no strong case for three booms on an antenna for the UHF bands anywhere in the world. Since Televes integrates amplification with their antennas, the publicized gain figures for their antennas are deceiving. On purely unamplified terms, computer models show that they are good but not great. The Televes antennas are known to be well constructed, and their integrated electronics are of high quality, but their performance is not actually particularly better than the best single-boom antennas from other European companies like Blake, Kathrien, and Triax with comparable amplification. In North America, an Antennas Direct 91XG outperforms it. So, while the Chinese tri-beam designs are superficially similar to Televes designs, they are not based on any particularly strong technical premise. That's why those tri-boomed knockoffs need to be looked at as a waste of two booms. ;)
There are a number of misconceptions here that I'd be happy to clarify if needed/wanted.
 

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This is a blast from the past! I think Stampeder commented on the Televes antenna (when making reference to chinese knock-offs) in 2015.

Post up some NEC2 input files, if you have them...
Zombie thread for sure, sorry. I read that comment suggesting that a triple boom design has no benefit in a number of places in the forum, which probably needs clarification.

Apologize the obvious, but just to start from the beginning, to better understand the behavior of Televes antennas, it is necessary to first understand how a Yagi antenna works. A Yagi antenna has a driven element (dipole) and a series of passive elements (reflector and directors) that are electromagnetically coupled to the dipole and to each other, with an inductive reactance the reflector (that blocks the signal in its direction) and capacitive reactance the directors (that favors the reception of the signal in its direction). This causes the antenna as a whole to favor reception in the direction of the directors and prevent reception in the direction of the reflector. The very basics thus far.

Given the nature of the coupling, the effectiveness of the passive elements decreases with the distance from the dipole, which means that the elements furthest from it have much less influence on the overall performance than the closest ones. As you can see in the figure I'm pasting below just as a basic example, from the sixth element on, the influence of the directors on the overall gain is very limited, the first five elements raise the gain by approximately 8dB and the next five elements only add another 1.5dB approx. So past certain point, which depends on the particular design, there are diminishing returns in what a longer antenna buys you.

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To improve the behavior of Yagi type antennas, Televes introduced more than 25 years ago the concept of several rows of directors stacked vertically, thereby achieving a greater number of directors close to the dipole, which allows to have higher perfomance antennas but smaller in size than conventional yagis.
As can be seen in the figure below representing the energy flow in an Ellipse antenna, the elements closest to the dipole are the most effective. With the vertical arrangement of the same we manage to have more elements near the dipole, increasing the performance of the antenna while maintaining a compact size.

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However, this requires a careful redesign of the dipole that allows for very precise coupling in the vertical plane. A typical simple dipole does not work with this structure. While Televes antenna designs have been copied over and over again -down to the color- most still don't get this part right and then the advantage of the multiple directors is wasted.
Hope this helps clarify some of this, and again apologies for resurrecting this.
 
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